This article was previously published in the Daily Climate
Deforestation in the Amazon is increasing the region’s vulnerability to droughts and fires, pushing it toward a “tipping point” that could cause rapid, large-scale destruction during dry years, according to a study published Monday.
The eight-year study, published in the Proceedings of the National Academy of Sciences, is the largest, longest-running experiment investigating the effects of fire on tropical forests.
It is also the first to show how fire and drought could lead to significant forest die-back in the Amazon, said Jennifer Balch, an assistant professor of geography at Penn State University who co-led the study.
Fires a major "disturbance" factor
“It’s only in the past couple of decades that fire has even been recognized as a major disturbance in Amazon forest,” Balch said. “Fire scientists are catching up with a phenomenon that’s happening so quickly as a result of frontier expansion and land-use changes.”
Large areas of tropical forest, particularly in the southeastern Amazon, are being logged and cleared for crops. Such practices thin the forest canopy, promote growth of invasive, quick-burning grasses, and cause warmer air to move in from cleared lands, drying the forest floor during times of little rain, according to the study.
Most climate models ignore fire effects
Many climate models predict an increase in temperature and less precipitation for the Amazon in the coming years. But most do not account for the compounding effects of fire, which are already causing forest dieback, Balch noted.
Those omissions could lead scientists to underestimate the amount of carbon released by dying trees and plants and lead to a less accurate picture of forest health, according to the study’s lead author, Paulo Monteiro Brando.
Emissions are so significant that researchers fear the Amazon could flip, becoming a net carbon emitter instead of a carbon sink.
Huge amounts of carbon missed?
“Big trees dying means more leaves on the ground and less canopy cover, and those are among the ingredients necessary for a high-intensity fire,” Brando said. “The more intense the fire, the more carbon that will be released. We may be missing huge amounts of carbon going into the atmosphere with these forest fires.”
A 2007 drought in the southeastern Amazon created conditions for intense wildfires that burned more forest than the amount of land deforested in the past four years, the scientists noted.
Deforestation rates dropping but still high
Brando pointed out that while Amazon deforestation remains high, it has dropped significantly in the past few years. But in places where forests are degraded and fragmented, especially areas adjacent to agricultural frontiers, drought and fire can have powerful consequences.
Reducing deforestation and the accidental spread of land-management fires, along with more effective firefighting, are among the strategies suggested by the study.
“It’s not that there is no solution,” Brando said. “There’s still a huge potential to manage the likelihood of these processes.”